US3518943A - Stable electrically ignitable explosive charges - Google Patents

Stable electrically ignitable explosive charges Download PDF

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Publication number
US3518943A
US3518943A US712012A US3518943DA US3518943A US 3518943 A US3518943 A US 3518943A US 712012 A US712012 A US 712012A US 3518943D A US3518943D A US 3518943DA US 3518943 A US3518943 A US 3518943A
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US
United States
Prior art keywords
charge
pellet
wire
conductor
nitrocellulose
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US712012A
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English (en)
Inventor
Jacques J Meers
Frederic C Merriam
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Emhart Enterprises Corp
USM Corp
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USM Corp
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Publication date
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Publication of US3518943A publication Critical patent/US3518943A/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42—AMMUNITION; BLASTING
    • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
    • F42B1/00—Explosive charges characterised by form or shape but not dependent on shape of container
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S102/00—Ammunition and explosives
    • Y10S102/70—Combustilbe cartridge

Definitions

  • a solid deflagrating charge of fibrous nitrocellulose has continuous burning surfaces defined by interconnected interstitial air spaces and includes firing means desirably in the form of an appropriate central electrical heating element leaving little or no residue on combusion.
  • the element is illustrated as of fine metal wire or graphite which, on carrying electrical energy, initiates ignition of the charge.
  • the charge will have been compacted to disc shape or other predetermined configuration suitable for sealing its firing chamber.
  • the cartridge though contemplated for use in explosively actuated stud driving tools or the like, is not limited to this field.
  • certain configurations of explosive pellets of this type are particularly well adapted to being ignited without the aid of a primer or diesel effect merely by physical impact, for instance that deliverable by a cocked firing pin.
  • This invention relates to solid, primerless low explosive formed charges. More particularly it is concerned with the provision of a stable, electrical igniter.
  • One application of this invention is as a power source in a fastener driving tool, a tool which could be simpler, perhaps less heavy, and probably less costly than the corresponding construction tool employing an impact ignitable charge of the type referred to in the copending application above mentioned.
  • the convenience of electrical ignition when coupled to relatively non-sensitive propellent fuel as herein disclosed finds utility in a broad range of applications including, but not limited to, propellants, pyrotechnic devices, primers, underwater forming or cutting devices, initiators etc. 1
  • the charge comprises, in combination, a body of compacted nitrocellulose fibres having a density less than that of nitrocellulose per se (and preferably for peak efficiency on the order of about 0.9 gram per cc.) and a conductor or heating element extending therethrough.
  • the hot wire, so called, for carrying electric current to initiate ignition desirably extends centrally through a formed pellet of the fuel, and preferably axially of a disc-shaped charge.
  • the Wire may be of metal such as that available under the trade name Nichrome (a nickel, chrome alloy), or be of graphite, or other suitable conductor having a heat developing resistance, and yet decomposable during the explosive reaction by reason of its dimensions without leaving any appreciable residue.
  • Nichrome nickel, chrome alloy
  • the preferred configuration of nitrocellulose pellet disclosed in the application 524,168 cited above facilitates impact ignition when the locality of impact is at a thin or recessed and reduced portion of the charge, the electrically ignitable formed charge herein disclosed need not be recessed or reduced, and hence greater power may be expected therefrom in a firing chamber of substantially the same size.
  • FIG. 1 is a perspective view of a pellet having a sector removed to reveal a central, axial igniting conductor, of graphite for instance;
  • FIG. 2 is a perspective of one-half of an explosive disc embodying our invention wherein a hot Wire conductor has its terminal portions radially disposed and embedded in opposed faces of the disc;
  • FIG. 3 is a view corresponding to FIG. 2 but showing a conductive wire with at least partly circular terminals abutting opposed faces of the charge, and
  • FIG. 4 is an enlarged detail view illustrating the interconnected, interstitial air spaces providing continuous burning surfaces on the flat, ribbon-like nitrocellulose fibres employed in the charges of FIGS. 1-3, and showing a portion of the central heating element.
  • FIG. 1 illustrates a disc-like charge or cartridge 10 of compacted nitrocellulose fibres 12 having a density in the range of from 0.6-1.6 gms./cc. Axially extending centrally between opposed planar end faces of the charge 10 is an electric, heat generating conductor in the form of a slender rod of graphite 14. It will be apparent that the charge 10 shown in FIG. 1, as well as those of FIGS. 2 and 3 to be described, may be compacted to a self-sustaining form which is non-circular in section if desired, the disc-like shape usually being preferred to enable substantially closed sealing of a cylindrical firing chamber which is to receive it.
  • the current conductor 14 will have its opposite ends, while the charge is confined in a substantial- 3 1y closed chamber, contacted by the electrodes of a circuit (not shown) connected to a suitable source of electric energy, for instance a suitable battery or a capacitor discharge circuit.
  • a suitable source of electric energy for instance a suitable battery or a capacitor discharge circuit.
  • the cartridge of FIG. 1 may be made in quantity from an elongated cylindrical form, an entire length of graphite being axially disposed in the fibres of nitrocellulose as they'are compacted from a slurry. Numerous individual charges of the desired degree of power (corresponding approximately to their selected individual axial lengths) may then be transversely severed from the full length prior to final drying and hardening, as by a jet of cutting fluid, for instance water.
  • a hot or bridge wire 20 may, for example, be of Nichrome (75% Ni. 12% Fe, 11% Cr, 2% Mn) or stainless steel having a diameter of about .003.
  • the wire need not be of a single strand but its melting point is preferably above that of copper which is 1082 C.
  • Its radial terminal portions 22, 22 are preferably lying exposed but partly embedded in opposite flat faces, respectively. These por tions are accordingly protected to some extent from being broken off, but are readily contactable by suitable electrodes of an ignition circuit.
  • An intermediate portion 24 of the Wire 20 preferably extends axially through a central portion of the pellet 16 and may be somewhat bowed as a consequence of angularly deflecting the terminal portions at the time of wire insertion, or as a result of pellet compaction. While in preferred form the conductor normally extends through a pellet, as above indicated, the electrodes of an ignition circuit for the pellet need not necessarily be disposed to contact opposite of other conductive, consumable material, that the lengthy, ribbonlike fibers of nitrocellulose (shown much enlarged) have numerous engagements or near-engagements with the heating element. Accordingly, experience indicates a very reliable and prompt ignition is assured once a firing circuit has been energized.
  • the following table shows, for three different sources of electric energy, the amount of energy required to effect explosion, and the delay in firing following closure of the firing circuit, for difierent combinations of nitrocellulose pellets and' their particular heating elements.
  • Energy requirements for effecting explosion of compacted nitrocellulose by electrical heating, in certain of the sample pellets indicated, are advantageously lower than what is required by the percussion ignition approach referred to above. It may be mentioned that When it is desired to preclude accidental firing by spurious electric currents, for instance to meet the so-called one watt of power and one ampere of current, 5 minute exposure but no fire test, the thickness or diameter of the heating element may be enlarged and/or the density of the nitrocellulose surrounding the element increased to the 1.3l.6 gms./cc. range.
  • a relatively fiuffy portion of nitrocellulose fibres having a reduced density perhaps on the order of about half that of the main body.
  • the portion of lower density nitrocellulose is referred to as fluffy," its actual density not being easily ascertaina'ble. This portion presumably facilitates ignition by reason of its having more or larger open air spaces contiguous with the heating element and between the ribbon-like fibres, a condition not illustrated in FIG. 4.
  • extremities of the conductor but may be disposed in a firing chamber for contact with operatively spaced localities of the conductor lying in or on an external surface portion of the pellet, for instance the terminal portion 22 or 28.
  • the pellet 18 of FIG. 3 has a bridge wire 26 like that shown in FIG. 2 except that its terminal portions 28, 28 have a circular configuration to provide more exposed surface for contact with an electrode.
  • the portions 28 need not be partly embedded but preferably should not extend appreciably from the exterior of the charge since this might result in its damage or a premature firing due to an earlier than intended electrical contact with a firing circuit.
  • the heating element may be of any of the types above mentioned or It will be understood that the representative pellets selected for the table shown were disc-shaped, had substantially constant thickness of about 0.1" and an outside diameter of about .336. They were usually custom made in the sense that they initially were provided with a bore for receiving the heating element and the main body of the pellet was thereafter compressed by a hollow die gradually to compact the fibres to cause them to close on the element; where the element-contacting fibres were to remain fiuffy only a light tamping was given.
  • An electrically ignitable solid low explosive charge comprising, in combination, fibrous nitrocellulose compacted to a density of less than 1.6 gms. per cc. to provide a pellet having substantially interconnected interstitial air spaces between its fibres to form continuous burning surfaces, and an electric conductor extending through the pellet between surfaces thereof for effecting its ignition by resistance heating, said conductor being of a material and dimensions selected to remain substantially intact during ignition of the fibres and produce substantially no residue due to combustion resultant from their explosion.
  • a charge as set forth in claim 1 wherein said conductor is a metal wire the terminal portions of which are exposed to provide contact ignition terminals on the opposite surfaces of the pellet, the melting point of the wire being higher than 1082 C.
  • An electrically ignitable caseless low explosive charge comprising, in combination, fibrous nitrocellulose compacted to a density of less than 1.6 grns. per cc. to provide a pellet having substantially interconnected interstitial spaces between its fibres to form continuous burning surfaces, and an electrical conductor in integral linear contact therewith at least along a suitably extension portion of the external surface of said pellet, said corresponding linearly contacting portion of the conductor having adequate resistance between two spaced points thereof such that when said two spaced points of the conductor are connected to a source of current and by reason of the nature of its material and its dimensions, to develop sufficient heat while intact to ignite and explode the remainder of the pellet thereby causing substantially all of the conductor to be consumed.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
  • Agricultural Chemicals And Associated Chemicals (AREA)
  • Air Bags (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Powder Metallurgy (AREA)
US712012A 1968-03-11 1968-03-11 Stable electrically ignitable explosive charges Expired - Lifetime US3518943A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US71201268A 1968-03-11 1968-03-11

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US3518943A true US3518943A (en) 1970-07-07

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US712012A Expired - Lifetime US3518943A (en) 1968-03-11 1968-03-11 Stable electrically ignitable explosive charges

Country Status (7)

Country Link
US (1) US3518943A (enrdf_load_stackoverflow)
BR (1) BR6907020D0 (enrdf_load_stackoverflow)
CH (1) CH487709A (enrdf_load_stackoverflow)
DE (1) DE1906573A1 (enrdf_load_stackoverflow)
ES (1) ES365136A1 (enrdf_load_stackoverflow)
FR (1) FR2003626A1 (enrdf_load_stackoverflow)
GB (1) GB1252984A (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3737986A (en) * 1971-11-26 1973-06-12 Western Electric Co Explosive bonding of workpieces
US5396951A (en) * 1992-10-16 1995-03-14 Baker Hughes Incorporated Non-explosive power charge ignition
US20060180223A1 (en) * 2003-06-16 2006-08-17 Biomerieux Electrically opended micro fluid-valve
US20220011286A1 (en) * 2020-05-12 2022-01-13 Rapiscan Systems, Inc. Sensitivity Traps for Electronic Trace Detection
US12411122B2 (en) * 2021-05-12 2025-09-09 Rapiscan Systems, Inc. Sensitivity traps for electronic trace detection having explosives or narcotics embedded in a plasticized polymer matrix

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1192668B (it) * 1978-03-02 1988-05-04 Dynamit Nobel Ag Perfezionamento nelle cariche propellenti in polvere
FR2853962B1 (fr) * 2003-04-16 2006-06-16 Snpe Materiaux Energetiques Dispositif d'initiation electrique d'une micro-charge pyrotechnique et microsysteme utilisant un tel dispositif
EP2989069A1 (de) 2013-04-25 2016-03-02 fischerwerke GmbH & Co. KG Elektrisch zündbarer hülsenloser treibsatz, dessen herstelung und verwendung

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE56470C (de) * L. GATHMANN in Chicago, III., V. St. A Verfahren zum Abkühlen von Geschützrohren nach dem Schufs unter Anwendung von flüssiger Kohlensäure
US571342A (en) * 1896-11-17 Shiell
US2829596A (en) * 1954-12-17 1958-04-08 Unexcelled Chemical Corp Tracking flares
US3210930A (en) * 1962-02-01 1965-10-12 Atlantic Res Corp Gas generator
US3340807A (en) * 1965-10-04 1967-09-12 Itt Exploding wire techniques
DE1258771B (de) * 1965-03-09 1968-01-11 Montage Technik Anstalt F Verfahren zum Zuenden von Treibladungen fuer pulverkraftbetriebene Bolzensetzwerkzeuge und Treibladung hierfuer

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE56470C (de) * L. GATHMANN in Chicago, III., V. St. A Verfahren zum Abkühlen von Geschützrohren nach dem Schufs unter Anwendung von flüssiger Kohlensäure
US571342A (en) * 1896-11-17 Shiell
US2829596A (en) * 1954-12-17 1958-04-08 Unexcelled Chemical Corp Tracking flares
US3210930A (en) * 1962-02-01 1965-10-12 Atlantic Res Corp Gas generator
DE1258771B (de) * 1965-03-09 1968-01-11 Montage Technik Anstalt F Verfahren zum Zuenden von Treibladungen fuer pulverkraftbetriebene Bolzensetzwerkzeuge und Treibladung hierfuer
GB1105663A (en) * 1965-03-09 1968-03-13 Hilti Ag Propellant or explosive charges, and method and apparatus for firing the same
US3340807A (en) * 1965-10-04 1967-09-12 Itt Exploding wire techniques

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3737986A (en) * 1971-11-26 1973-06-12 Western Electric Co Explosive bonding of workpieces
US5396951A (en) * 1992-10-16 1995-03-14 Baker Hughes Incorporated Non-explosive power charge ignition
US20060180223A1 (en) * 2003-06-16 2006-08-17 Biomerieux Electrically opended micro fluid-valve
US7159618B2 (en) 2003-06-16 2007-01-09 Bio{acute over (m)}erieux Electrically opened micro fluid valve
US20220011286A1 (en) * 2020-05-12 2022-01-13 Rapiscan Systems, Inc. Sensitivity Traps for Electronic Trace Detection
US12411122B2 (en) * 2021-05-12 2025-09-09 Rapiscan Systems, Inc. Sensitivity traps for electronic trace detection having explosives or narcotics embedded in a plasticized polymer matrix

Also Published As

Publication number Publication date
GB1252984A (enrdf_load_stackoverflow) 1971-11-10
ES365136A1 (es) 1971-01-16
BR6907020D0 (pt) 1973-01-09
FR2003626A1 (enrdf_load_stackoverflow) 1969-11-14
DE1906573A1 (de) 1969-10-02
CH487709A (de) 1970-03-31

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